Switching regulators are widely used for powering modem electronic devices. For example, a power source, say, a battery or fuel cell may provide a voltage (Vin, sometimes also called a source) from which it is desired to provide a steady voltage (Vout, sometimes also called a drain) to an application load.
Unfortunately, however, prior art switching regulators have architectures that are not good at handling changing load conditions in power managed systems where the load currents vary drastically between different system operating modes.
For example, many prior art switching regulators simply employ one or more pulse skipping modes (a form of pulse frequency modulation, or PFM) to cope with a demand for less than their designed maximum power consumption. This results in less than ideal power conversion efficiency because the internal drive strength still remains strong to accommodate the potential maximum load. Furthermore, the pulse skipping nature of such PFM switching regulators can cause slower response to rapid load current changes, which tends to create excessive output voltage ripple.
Other prior art switching regulators employ pulse duration changing modes (pulse width modulation, or PWM) to cope with demands for less than design-maximum power consumption. This can be an improvement over PFM approaches in some applications, and some integrated circuit manufactures today provide devices that can selectively employ PWM or PFM to drive external power semiconductors.
Unfortunately, the PWM approach as implemented in prior art switching regulators is still not particularly good at handling drastically changing load conditions in different system operating modes. The design of these regulators is still focused on maximum power consumption and, when a load is not requiring this, these regulators also have less than optimal power conversion efficiency.
FIG. 1a (prior art) is a block diagram stylistically depicting a generic conventional switching regulator. The regulator depicted here is buck type (Vin>Vout), but the comments here generally apply to boost type regulators (Vin<Vout), and buck/boost types as well. The regulator depicted here also employs both a p-type and an n-type transistor. Although not especially relevant, some conventional switching regulator designs simply use a diode in place of the n-type transistor shown in FIG. 1a. FIG. 1b (background art) stylistically depicts the waveforms the Ctrl block in FIG. 1a might employ. At full load the drive signals to the power switching transistors will resemble the regular clock signal. That is, it will be roughly symmetrical (in practice, slightly reduced pulse widths may be used to avoid overlap issues). In a PFM based design at a lower than maximum load, the drive signals to the power switching transistors will resemble the middle signal shown. And in a PWM based design at a lower than maximum load, the drive signals to the power switching transistors will resemble the lower signal shown.
Briefly summarizing, these two traditional approaches can be viewed as clock changing and duty cycle changing. And neither of these approaches is good at handling drastically changing load conditions in different system operating modes, which is increasingly the case in modem electronic devices. In a “lines powered” application such inefficiency may be tolerable, albeit undesirable, but in a battery or other limited power source application such inefficiency can lead to an entire “parade of horribles.” For example, power inefficiency will shorten battery life for disposable batteries, or shorten charge life for rechargeable batteries. Using unduly large batteries, or replacing smaller ones unduly often, can therefore result in waste disposal problems. Many electronic component and device manufactures today are concerned about this, out of environmental awareness and increasingly due to outright governmental regulation. Indirectly, power inefficiency can also result in thermal issues. For instance, some laptop computers today are notorious for burning their user's laps if some form of extra insulation is not used.
Accordingly, improved architectures for switching regulators that serve changing load conditions remain desirable and can expect to be well received by electronics manufacturers, users of the products from those manufacturers, and by those concerned with the general public good.